KR101514221B1 - manufacturing method of multi layer polyimide flexible metal-clad laminate - Google Patents

Abstract

The present invention relates to a method for producing a flexible metal laminate having a multilayer polyimide structure, which comprises a metal foil and a multilayer polyimide formed on one or both sides of the metal foil, wherein the multilayer polyimide having different coefficients of linear thermal expansion and the multilayer polyimide And a gradient layer in which a gradient is formed between the multi-layer polyimide layers according to a difference in linear thermal expansion coefficient between the polyimide layers, and a method for manufacturing the multi-layer polyimide flexible metal-clad laminate. The flexible metal laminate of the multilayer polyimide structure according to the present invention can provide a flexible metal laminate for a printed circuit board which is excellent in adhesion to metal foil and dimensional stability while solving the problem of foaming between polyimide layers.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a flexible metal laminate having a multilayer polyimide structure,

The present invention relates to a multilayer polyimide flexible metal laminate and a method of manufacturing the same, and more particularly, to a method for producing a polyimide laminated on a metal foil and two or more surfaces of the metal foil and having excellent adhesion between the metal foil and the polyimide layer Layer polyimide flexible metal clad laminate capable of suppressing the foaming phenomenon occurring at an interface between polyimide layers having different coefficient of linear thermal expansion.

[0003] As miniaturization, multifunctionalization, and thinning of electronic devices have been made, circuit boards used in electronic devices are required to be further densified. In order to meet such demands, a method of multilayering circuit boards has been used. In addition, a flexible printed circuit board (flexible printed circuit board) having flexibility to allow a circuit board to be installed in a narrow space may be used, or a circuit having a narrow line width may be used to obtain a large number of circuits in the same space.

Soldering as a method for multilayering a circuit board has a problem of causing environmental problems. Accordingly, there is a demand for an adhesive having high adhesive strength, high heat resistance and low moisture absorption rate for multilayering of circuit boards. However, a metal laminate plate in which a conventional acrylic or epoxy adhesive is used to adhere a polyimide film to a metal foil is insufficient for a circuit board requiring multilayering, flexibility, high adhesive strength, and high heat resistance. Therefore, a 2-layer copper clad laminate (2CCL) type flexible metal laminate which directly bonds a polyimide layer and a metal foil without using an adhesive has been developed. Such a metal laminate is a flexible circuit board material having excellent thermal stability, durability and electrical characteristics as compared with 3CCL (3-Layer Copper Clad Laminate) in which a metal layer and a polyimide layer are bonded using a conventional adhesive.

 The 2-layer copper clad laminate (2CCL) type flexible metal laminate can be roughly divided into a cross-section metal laminate composed of a metal foil and a polyimide layer and a double-side metal laminate having a polyimide layer between two metal foils. The polyimide layer is generally composed of two or more layers of polyimide composed of polyimide having a different coefficient of linear thermal expansion, rather than a single layer, in order to satisfy characteristics such as adhesion with metals and dimensional stability. Korean Patent Laid-Open No. 10-2009-0066399 (Patent Document 1) discloses a polyimide metal foil laminate having different thermal expansion coefficients.

Generally, in order to form a multi-layered polyimide, the process of coating and drying the polyamic acid varnish, which is a polyimide precursor, on the metal foil as many times as the number of layers to be laminated is repeated. Particularly, in order to increase the adhesion to a metal foil, a polyimide precursor layer having a high coefficient of linear thermal expansion such as polyimide is first coated on a metal foil, dried, and a polyimide precursor layer having a low coefficient of linear thermal expansion is coated , And dried. In this case, since the polyimide precursor layer dried first is in a solidified state, the interlayer intermixing rarely takes place during coating and drying of the coated polyimide precursor layer, so that the coefficient of linear thermal expansion along the thickness direction becomes the interface between the polyimide layers As shown in FIG. (Hereinafter, referred to as "curing process"). At this time, the interfacial stress generated at the interface of the polyimide layer having different coefficients of linear thermal expansion Resulting in defects such as foaming and, more severely, delamination. This foaming problem can be suppressed by lowering the heating rate to the maximum temperature during curing or increasing the total curing time. However, when a roll-to-roll type curing machine is used, the curing time This short time and the residence time in the curing machine are directly related to the productivity, so another solution is required.

Korean Patent Publication No. 10-2009-0066399

Disclosed is a flexible metal laminate comprising a metal foil and a polyimide layer laminated on at least one surface of the metal foil, wherein the metal foil has excellent adhesion to the metal foil and dimensional stability A flexible metal clad laminate having a multilayer polyimide structure capable of suppressing a foaming phenomenon occurring during curing in the process of laminating polyimide, and a method for manufacturing the same.

Layer polyimide having a different coefficient of linear thermal expansion between the metal foil and the metal foil and between the polyimide layers of the multi-layer polyimide having different coefficients of linear thermal expansion and between the multi-layer polyimide layers And a gradient layer in which a gradient is formed in the metal layer.

Further, according to the present invention,

A polyimide precursor layer having different coefficient of linear thermal expansion different from that of the metal foil and the metal foil on both sides or both sides of the metal foil is successively laminated in two or more layers without drying and dried and cured to form a gradient between the multilayer polyimide layers Forming a polyimide layer comprising a formed gradient layer; The present invention also provides a method for manufacturing a multilayer polyimide flexible metal laminate.

In the present invention, in the production of a metal foil and a multilayer polyimide laminated on two or more surfaces of the metal foil, two or more polyimide layers having different coefficients of linear thermal expansion are subjected to a multi- It is possible to provide a flexible metal laminate for a printed circuit board excellent in adhesion to a metal foil and dimensional stability while solving the problem of foaming between polyimide layers by successively laminating precursor layers, followed by drying and imidization.

A flexible metal laminate made of three layers of polyimide structure,
Figure 1 shows a cross-sectional view of a laminate made by successively multi-coating three different polyimide precursor layers, followed by drying and imidization.
DESCRIPTION OF THE DRAWINGS -
10: a first polyimide layer having a high thermal expansion characteristic
20: a second polyimide layer having low thermal expansion characteristics
30: a third polyimide layer having a high thermal expansion characteristic
40: a gradient layer (mixed layer) of the first polyimide layer and the second polyimide layer,
50: a gradient layer (mixed layer) of the second polyimide layer and the third polyimide layer,
60: Metal foil
FIG. 2 is a schematic view showing a structure in which the coefficient of linear thermal expansion between the polyimide layers having different thermal expansion characteristics is not changed abruptly due to the mixing effect in the gradient layer, and has a gradient. Here, 'Mixing' denotes the mixed portion of the continuous polyimide layer.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The present invention relates to a metal foil and a multilayer polyimide formed on one or both surfaces of the metal foil, wherein the multilayer polyimide having a different coefficient of linear thermal expansion and the polyimide layer of each of the multilayer polyimide have a multilayer poly And a gradient layer in which a gradient is formed between the intermediate layer and the intermediate layer.

More specifically, the multi-layer polyimide has an n-th (n > = 1) polyimide layer, an n + 1 (n > = 1) polyimide layers, wherein the n < th > and (n + l) polyimide layers have a gradient according to a difference in linear thermal expansion coefficient.

At this time, the multilayer polyimide layer has a coefficient of linear thermal expansion of 10 to 100 ppm / K.

The multilayer polyimide layer according to the present invention is characterized in that the difference in coefficient of linear thermal expansion between layers is 10 to 90 ppm / K.

In the multilayer polyimide flexible metal clad laminate according to the present invention, the polyimide layer includes a gradient layer formed between the multilayer polyimide layers according to the difference in linear thermal expansion coefficient.

That is, in the multilayer polyimide soft metal laminates according to the present invention, since the different polyimide precursor layers are successively laminated, the layers are dried together without being solidified. In this case, as the solvent evaporates, the polyimide precursor located on the lower layer rises with the solvent and is mixed with the polyimide precursor located on the upper layer. As a result, the interface between the two layers disappears and a mixed layer of several microns thick . Due to the formation of this mixed layer, the change in coefficient of linear thermal expansion in the thickness direction becomes gentle at the interface between the layers. In the present invention, this is defined as a gradient. Such a gradient layer is schematized in Fig. Wherein the gradient layer 40 of the first and second polyimide layers is formed by penetration into a second polyimide layer where the first polyimide layer is the top layer and the gradient layer 50 of the second and third polyimide layers And the second polyimide layer is formed by penetration into the third polyimide layer as the upper layer.

  As a result, in the course of curing of the polyimide precursor layers, the gradient layer (mixed layer) serves to reduce the occurrence of interfacial stress due to the thermal expansion change of each layer. As a result, foaming phenomenon or interfacial peeling Delamination phenomenon is significantly reduced. FIG. 2 schematically illustrates a gradient layer having a gradient between multilayer polyimide layers according to the difference in linear expansion coefficient.

The polyimide layer according to the present invention is characterized in that the thickness of each layer is 1 to 30 占 퐉.

In the present invention, the metal foil is preferably selected from copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, or an alloy thereof. Generally, copper is widely used.

Next, the polyimide precursor solution contained in the polyimide precursor layer constituting the component of the present invention will be described in detail.

The polyimide precursor solution forms a polyimide precursor layer through lamination, and the polyimide precursor layer is dried and cured to form a polyimide layer, thereby forming a polyimide layer.

The polyimide precursor solution in the present invention can be prepared in the form of a varnish obtained by mixing dianhydride and diamine in a proper organic solvent at a molar ratio of 1: 0.9 to 1: 1.1. The varnish thus obtained is coated on a metal plate at least once and dried to form a polyimide precursor layer. In the present invention, when a polyimide precursor solution is prepared, a polyimide resin having a desired coefficient of thermal expansion is obtained by adjusting the mixing ratio of dianhydride and diamine, or mixing ratio of dianhydride or diamine, and adjusting the kind of dianhydride and diamine selected .

Examples of the dianhydride suitable for the present invention include PMDA (pyromellitic dianhydride)

BPDA (3,3 ', 4,4'-biphenyltetracarboxylic dianhydride), BTDA (3,3', 4,4'-benzophenone tetracarboxylic dianhydride), ODPA (4,4 ' -Oxydiphthalic anhydride), ODA (4,4'-diaminodiphenyl ether), BPADA (4,4 '- (4,4'-isopropylbiphenoxy) biphthalic anhydride) , 6FDA (2,2'-bis- (3,4-dicarboxyphenyl) hexafluoropropane dianhydride), and TMEG (ethylene glycol bis (anhydro-trimellitate) Can be used.

Examples of the diamine suitable for the present invention include PDA (p-phenylenediamine), m-PDA (m-phenylenediamine), 4,4'-ODA (4,4'-oxydianiline) ODA (3,4'-oxydianiline), BAPP (2,2-bis (4- [4- aminophenoxy] -phenyl) propane), TPE-R (1,3- ) Benzene), BAPB: 4,4'-bis (4-aminophenoxy) biphenyl, m-BAPS (2,2- 3'-dihydroxy-4,4'-diaminobiphenyl) and DABA (4,4'-diaminobenzanilide) can be used.

In the present invention, it is possible to add a small amount of dianhydride, diamine, or other compound other than the above-mentioned compounds, if necessary.

Suitable organic solvents for preparing the polyimide precursor solution in the present invention include N-methylpyrrolidinone (NMP), N, N-dimethylacetamide (DMAc), tetrahydrofuran (THF), N, But are not limited to, amides (DMF), dimethylsulfoxide (DMSO), cyclohexane, acetonitrile, and mixtures thereof.

It is preferable that the polyimide precursor is present in an amount of 5 to 30% by weight in the total solution. When the amount is less than 5% by weight, unnecessary use of the solvent increases. When the amount exceeds 30% by weight, the viscosity of the solution becomes excessively high, Can not.

In order to facilitate application or curing or to improve other physical properties, additives such as antifoaming agents, gel inhibitors, curing accelerators and the like may be further added.

Hereinafter, a method for producing the multilayer polyimide flexible metal laminate plate of the present invention will be described in detail.

The present invention relates to a metal foil and a metal foil which are formed by laminating two or more layers of a polyimide precursor layer having different coefficients of linear thermal expansion different from each other on both sides or both sides of a metal foil after curing and drying and curing the same, Forming a polyimide layer including a gradient layer having a gradient formed therein; The present invention also provides a method for manufacturing a multilayer polyimide flexible metal laminate.

In the method for producing a flexible metal laminate according to the present invention, the polyimide layer has a coefficient of linear thermal expansion of 10 to 100 ppm / K. If the coefficient of linear thermal expansion is less than 10 ppm / K or more than 100 ppm / K, the adhesion between the metal foil and the polyimide may decrease due to the difference in the coefficient of linear thermal expansion between the metal foil and the peeling phenomenon at the interface between the metal foil and the drying and curing process .

The polyimide layer according to the present invention is characterized in that the difference in coefficient of linear thermal expansion between layers is 10 to 90 ppm / K.

The thickness of each layer of the polyimide layer according to the present invention is preferably 1 to 30 占 퐉. If it is less than 1 μm, it is difficult to apply by a general coating method, and if it is more than 30 μm, a curl phenomenon of the film due to evaporation of the solvent during drying and curing process becomes worse.

The metal foil according to the present invention is selected from copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten or alloys thereof.

In the above manufacturing method, different polyimide precursor layers are laminated successively by applying a multi-coating method. Continuous lamination means not involving an interlayer drying step. The lamination is selected from knife coating, roll coating, slot die coating, lip die coating, slide coating and curtain coating.

Hereinafter, the 'lamination' of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a method for producing a flexible metal laminate having a three-layered polyimide structure, in which three different polyimide precursor layers are successively multi-coated without a drying step, followed by drying and imidization, Sectional view of a layered product in which a gradient layer (a mixed layer) is formed between the intermediate layers.

Coating methods applicable to the present invention include knife coating, roll coating, slot die coating, lip die coating, slide coating and curtain coating a curtain coating method, or the like, or a method of sequentially laminating two or more coating methods successively using multi-die coating or the like, and there is no great limitation.

The present invention will be described in more detail with reference to the following more specific examples and comparative examples of the present invention. However, the present invention is not limited to the following examples and comparative examples, and various embodiments can be implemented within the scope of the appended claims. Only the following embodiments are intended to facilitate the practice of the invention to those skilled in the art without departing from the spirit of the invention.

Abbreviations used in the examples are as follows.

DMAc: N-dimethylacetamide (N, N-dimethylacetamide)

BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic acid dianhydride

(3,3 ', 4,4'-biphenyltetracarboxylic acid dianhydride)

PDA: para-phenylenediamine (p-phenylenediamine)

ODA: 4,4'-diaminodiphenylether (4,4'-diaminodiphenylether)

BAPB: 4,4'-bis (4-aminophenoxy) biphenyl

(4,4'-bis (4-aminophenoxy) biphenyl)

The physical properties mentioned in the present invention were measured according to the following method.

1. Coefficient of Thermal Linear Expansion (CTE)

 The coefficient of linear thermal expansion was obtained by averaging the values between 100 ° C and 250 ° C of the measured thermal expansion values by raising the temperature to 400 ° C at a rate of 5 ° C per minute using a TMA (Thermomechanical Analyzer).

2. Adhesion between polyimide resin and metal foil

In order to measure the peel strength between the polyimide resin and the metal layer, the metal layer of the laminate was patterned at a width of 1 mm, and then the peel strength of 180 ˚ was measured using a universal testing machine (UTM).

3. Dimensional change rate after etching

 Followed by 'Method B' of IPC-TM-650, 2.2.4. MD, and TD were 275 mm x 255 mm, and the distance between each hole was measured after repeating the measurement. The holes were drilled at four corners of a square specimen and stored in a constant temperature and humidity chamber at 23 ° C and 50% RH for 24 hours. After that, the metal foil was etched and the distance between the holes was measured again after being stored in a constant temperature and humidity chamber of 23 ° C and 50% RH for 24 hours. The change rates of the measured values in the MD and TD directions were calculated.

4. Foam observation

Five averages of the number of foams generated within 50 cm x 50 cm were recorded. In the case of no foaming, it was recorded as 'none'. In the case of foaming on the whole surface, it was recorded as 'interfacial peeling'.

 [Synthesis Example 1]

 To 211,378 g of the DMAc solution, 12,312 g of PDA and 2,533 g of ODA were stirred in a nitrogen atmosphere to completely dissolve, and 38,000 g of BPDA as dianhydride was added in several portions. Thereafter, stirring was continued for about 24 hours to prepare a polyamic acid solution. The polyamic acid solution thus prepared was cast into a film having a thickness of 20 탆, heated to 350 캜 for 60 minutes, and held for 30 minutes to be cured. The measured coefficient of linear thermal expansion was 13.4 ppm / K.

[Synthesis Example 2]

 To 117,072 g of the DMAc solution, 3.278 g of PDA and 2.024 g of ODA were stirred in a nitrogen atmosphere to completely dissolve, and 12,000 g of BPDA as dianhydride was added in several portions. Thereafter, stirring was continued for about 24 hours to prepare a polyamic acid solution. The polyamic acid solution thus prepared was cast into a film having a thickness of 20 탆, heated to 350 캜 for 60 minutes, and held for 30 minutes to be cured. The measured coefficient of linear thermal expansion was 19.5 ppm / K.

[Synthesis Example 3]

 2.187 g of PDA and 4.047 g of diamine were dissolved in 117.072 g of the DMAc solution by stirring in a nitrogen atmosphere and 12,000 g of BPDA as dianhydride was added in several portions. Thereafter, stirring was continued for about 24 hours to prepare a polyamic acid solution. The polyamic acid solution thus prepared was cast into a film having a thickness of 20 탆, heated to 350 캜 for 60 minutes, and held for 30 minutes to be cured. The measured coefficient of linear thermal expansion was 34.0 ppm / K.

[Synthesis Example 4]

 To 11,572 g of the DMAc solution, 948 g of diamine of BAPB was completely dissolved by stirring in a nitrogen atmosphere, and then 757 g of BPDA was added as dianhydride. Thereafter, stirring was continued for about 24 hours to prepare a polyamic acid solution. The polyamic acid solution thus prepared was cast into a film having a thickness of 20 탆, heated to 350 캜 for 60 minutes, and held for 30 minutes to be cured. The measured coefficient of linear thermal expansion was 65.1 ppm / K.

[Example 1]

A polyamic acid solution prepared through [Synthesis Example 1] was coated on a rolled copper foil (Rz = 1.0 mu m) having a thickness of 12 mu m using a lip die so as to have a thickness of 3 mu m after curing, The polyamic acid solution prepared through Synthesis Example 4 and the polyamic acid solution prepared through Synthesis Example 1 were continuously coated with a multi slot die so that the thickness after curing was 20 占 퐉 and 3 占 퐉, Respectively. This was allowed to stand in a drier at 130 DEG C for 15 minutes and then cured in a roll to roll curing machine to raise the temperature from 150 DEG C to 390 DEG C for 10 minutes and stay at 390 DEG C for 5 minutes. The results are shown in Table 1.

[Example 2]

A polyamic acid solution prepared through [Synthesis Example 1] was coated on a rolled copper foil (Rz = 1.0 mu m) having a thickness of 12 mu m using a lip die so as to have a thickness of 3 mu m after curing, The polyamic acid solution prepared through Synthesis Example 4 and the polyamic acid solution prepared through Synthesis Example 1 were continuously coated with a multi slot die so that the thickness after curing was 20 占 퐉 and 3 占 퐉, Respectively. This was allowed to stand in a drier at 130 DEG C for 15 minutes and then undergo a curing process in a roll to roll curing machine to raise the temperature from 150 DEG C to 390 DEG C for 5 minutes and stay at 390 DEG C for 5 minutes. The results are shown in Table 1.

[Comparative Example 1]

The polyamic acid solution prepared through [Synthesis Example 1] was coated on a rolled copper foil (Rz = 1.0 占 퐉) having a thickness of 12 占 퐉 using a lip die so as to have a thickness of 3 占 퐉 after curing, Lt; 0 > C for 5 minutes to form a first polyimide precursor layer. The polyamic acid solution prepared through [Synthesis Example 4] was coated thereon and dried to form a second polyimide precursor layer under the same conditions so that the thickness after curing became 20 탆. The polyamic acid solution prepared through Synthesis Example 1 was further coated thereon and dried to form a third polyimide precursor layer under the same conditions so that the cured polyimide solution had a thickness of 3 占 퐉 to form a third polyimide precursor layer. (roll to roll) curing machine to raise the temperature from 150 ° C to 390 ° C for 10 minutes and to let the cured product stay at 390 ° C for 5 minutes. The results are shown in Table 1.

[Comparative Example 2]

The polyamic acid solution prepared through [Synthesis Example 1] was coated on a rolled copper foil (Rz = 1.0 占 퐉) having a thickness of 12 占 퐉 using a lip die so that the thickness after curing became 3 占 퐉, Min to form a first polyimide precursor layer. The polyamic acid solution prepared through [Synthesis Example 4] was coated thereon and dried to form a second polyimide precursor layer under the same conditions so that the thickness after curing became 20 탆. The polyamic acid solution prepared through Synthesis Example 1 was further coated thereon and dried to form a third polyimide precursor layer under the same conditions so that the cured polyimide solution had a thickness of 3 탆 so that the precursor layer of these polyimides was heated to 150 캜 To 390 < 0 > C for 5 minutes and to remain at 390 < 0 > C for 5 minutes. The results are shown in Table 1.

[Comparative Example 3]

The polyamic acid solution prepared through [Synthesis Example 2] was coated on a rolled copper foil (Rz = 1.0 mu m) having a thickness of 12 mu m using a lip die so that the thickness after curing was 3 mu m, Min to form a first polyimide precursor layer. The polyamic acid solution prepared through [Synthesis Example 4] was coated thereon and dried to form a second polyimide precursor layer under the same conditions so that the thickness after curing became 20 탆. The polyamic acid solution prepared through [Synthesis Example 2] was further coated thereon and dried to form a third polyimide precursor layer under the same conditions so that the cured polyimide solution had a thickness of 3 탆, and then the precursor layer of these polyimides was heated to 150 캜 To 390 < 0 > C for 10 minutes and allowed to stand at 390 < 0 > C for 5 minutes. The results are shown in Table 1.

[Comparative Example 4]

The polyamic acid solution prepared through [Synthesis Example 3] was coated on a rolled copper foil (Rz = 1.0 mu m) having a thickness of 12 mu m using a lip die so that the thickness after curing became 3 mu m, Min to form a first polyimide precursor layer. The polyamic acid solution prepared through [Synthesis Example 4] was coated thereon and dried to form a second polyimide precursor layer under the same conditions so that the thickness after curing became 20 탆. The polyamic acid solution prepared through [Synthesis Example 3] was further coated thereon and dried to form a third polyimide precursor layer under the same conditions so as to have a thickness of 3 탆 after curing, and then the precursor layer of these polyimides was heated to 150 ° C To 390 < 0 > C for 10 minutes and allowed to stand at 390 < 0 > C for 5 minutes. The results are shown in Table 1.

[Table 1]

As shown in the table, the multilayer polyimide flexible metal clad laminate according to the present invention has excellent adhesion, has a small dimensional change rate, and has good appearance after curing.

Claims (12)

delete delete delete delete delete delete After curing on one side or both sides of the metal foil and the metal foil, a different polyimide precursor layer having a coefficient of linear thermal expansion of 10 to 100 ppm / K in each layer and a difference in the coefficient of linear thermal expansion between layers of 40 to 90 ppm / K is dried Forming a polyimide layer including a gradient layer having a gradient between the multilayer polyimide layers according to the difference in coefficient of linear thermal expansion; , The thickness of each polyimide layer is 1 to 30 占 퐉,
Wherein the curing satisfies the following formula (1): " (1) "
[Formula 1]
5 < _Tmin ≤ 10
(In the above formula 1, T _min is the temperature rise time from 150 to 390 ° C.) delete delete delete 8. The method of claim 7,
Wherein the metal foil is any one selected from copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, and alloys thereof. 8. The method of claim 7,
Wherein said lamination is one or two or more selected from knife coating, roll coating, slot die coating, lip die coating, slide coating and curtain coating.

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